320 SPIRIFERID^. 



of the spiral coues in the type same as in Zygospira, the base of 

 each spiral cone being obliquely inclined towards the bottom 

 and sides of the ventral valve ; there are about four coils in 

 each spiral cone ; the primary stems of the spirals are attached 

 to the hinge-plate of the dorsal valve ; and after extending 

 parallel to each other for a short distance, they bend at right- 

 angles abruptly towards the lateral portions of the beak, and 

 form two large curves facing the lateral portions of the valve ; 

 just before reaching their farthest extension in front they give 

 off a semicircular band or loop, w^hich is directed upwards 

 towards the beak, and is exterior to the spiral cones on their 

 dorsal side. 



Family SPIRIFERID^. 



Shell furnished internall}^ with two calcareous spiral processes 

 (apophyses) directed outwards towards the sides of the shell, and 

 destined for the support of the oral arms, which must have been 

 fixed immovably ; the spiral lamellae are sometimes spinulose, 

 indicating the existence of rigid cirri, especially on the front of 

 the whorls ; valves articulated by teeth and sockets. 



Spirifer, Sowerby, 1815. 



Syn. — Trigonotreta, Konig, 1825. Choristites, Fischer, 1825. 

 Delthyris, Dalman, 1828. Fusula, Reticularia, Brachythyris, 

 M'Coy, 1844. 



Distr. — 300 sp. Lower Silurian — Trias ; Arctic America — 

 Chili, Falkland Islands, Europe, China, Thibet, Australia, Tas- 

 mania. In China these and other fossils are used as medicine. 

 S. striatus. Mart, (cxxxvii, [)5, 96). S. Wolcotti, Sowerby 

 (cxxxvii, 97). 



Shell transversely oval or elongated, trilobed, beaked, biconvex, 

 with a dorsal ridge and ventral furrow; hinge-line wide and 

 straight; area moderate, striated across; foramen angular, open 

 in the young, afterwards progressively closed ; ventral valve with 

 prominent hinge-teeth, and a central muscular scar, consisting of 

 the single adductor flanked by two cardinal impressions ; dorsal 

 valve with a small cardinal process, a divided hinge-plate, and 

 two conical spires directed outwards and nearlj^ filling the cavity 

 of the shell ; crura united by an oral loop. The shell and spires 

 are sometimes silicified in limestone, and may be developed by 

 means of acid. In S. mosquensis the dental plates are prolonged 

 nearly to the front of the ventral valve. 



spiRiFERiNA, d'Orbigny, 184'7. (Mentzelia, Quenst., 1811.) 

 Shell punctate, external surface spinulose; foramen covered by 

 a pseudo-deltidium ; interior of ventral valve with a prominent 

 septum, rising from the adductor scar. 29 sp. Cari3. — Lower 

 Oolites; Britain, France, Germany, South America. S. rostraia, 

 Schloth. (cxxxvii, 98-100). 



